This circuit was found in Radio Electronics from the 90s. It converts capacitance into frequency in order to obtain a proportional voltage that can be measured in a common multimeter.
This useful power supply was found in an 1985 Italian publication, but can still be assembled...
This dimmer for 12 V incandescent lamps was found in a 1966 General Electric documentation. The circuit has...
With this circuit any number of 4017 integrated circuits can be connected in series. The circuit is...